HPE EVA Storage

8 disks in a disk group


8 disks in a disk group

Best practices says you should have a multiple of 8 disks in your disk group. What is the performance impact if your disk group does not have a multiple of 8 disks in the group? Say 10? We've got an eva 6400 with 300 gb drives.


P.S. This thread has been moved from Disk to Storage Area Networks (SAN) (Enterprise). -HP Forum Moderator

Steven Clementi
Honored Contributor

Re: 8 disks in a disk group

I don;t think there is any major performance hit in regards to having a non multiple of 8 amount of disks in the group.

This best practice is more for protection of data since the controllers try to groups disks in multiples of 8 for creation of Redundant Storage Sets.

I think that any number of disks more than 8 would still give you more total i/o thus increasing performance... negating much of any effect that not having a multiple of 8 disks would have on the array.

Steven Clementi
HP Master ASE, Storage, Servers, and Clustering
MCSE (NT 4.0, W2K, W2K3)
VCP (ESX2, Vi3, vSphere4, vSphere5, vSphere 6.x)
NPP3 (Nutanix Platform Professional)

Re: 8 disks in a disk group

Hi all
For more performance , add as many disks as you want in a disk group.
Multiple of 8 is for redundancy inside the group. If you can, spread your groups throughout the shelves you have in multiple of 8 disks
Esteemed Contributor

Re: 8 disks in a disk group

the best data protection across the RSSs in multiples of 8 is only fully effective if you have at least 8 disk enclosures, if you have less then you would end up with 2 disks from the same RSS in one shelf so loss of a shelf would likely cause data loss. obvouusly you would need all the disks in place when creating the disk group in order for the controllers to stripe the RSSs vertically :) This is in addition to the Vraids and happens at a lower level.
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Neil Cummings
Occasional Advisor

Re: 8 disks in a disk group

An RSS is like a mini RAID 5 set within the VRAID set and is grouped in sets of 8 disks and the final RSS ranges from 6-11 disks.

That said, you would most likely have a very slight performance increase by having 10 disks instead of 8 since there would be more spindles in just one RSS. This applies up to and including 11 disks, since that is the max size of an RSS. If you had 12 disks the EVA would form two RSS groups of 6 disks each.

As Greybeard quite rightly states, its best though to have multiples of 8 drives in your diskgroup(s) and also to have 8 drive shelves, that way you build what is referred to as a robust EVA which can theoretically handle one full drive shelf failure.